Switch mode power supplies and integrated circuits are presented to provide a dc output voltage signal using high and low side switches, with a switching control circuit to turn off the high side switch and engage an active shunt circuit to provide a reduced voltage to continue converter operation to accommodate high input voltage transients when the dc input voltage exceeds a threshold voltage without requiring an oversized low side switch for improved efficiency through reduced switching and conduction losses in normal operation.
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20. A power supply circuit to provide a dc output voltage signal, comprising: a high side switching device coupled between a dc input node and a switching node, the switching node connected to an output inductor to provide the dc output voltage signal at an output node; a low side switching device coupled between the switching node and a constant voltage node; a control circuit operative when a dc input voltage at the dc input node is less than a threshold voltage to operate the first and second switching devices in alternating fashion to regulate the dc output voltage signal; and a second supply circuit coupled to receive the dc input voltage, the second supply circuit including a capacitor and a plurality of transistors selectively operative to provide a voltage signal at a level less than the dc input voltage at the dc input node; the control circuit operative when the dc input voltage is greater than the threshold voltage to turn off the high side switching device, and to operate the low side switching device and at least one of the plurality of transistors of a shunt circuit to provide to control the dc output voltage signal.
16. A power conversion system, comprising:
a dc-DC converter circuit, including:
a dc input node to receive a dc input voltage;
an output node to provide an output voltage signal;
a first switching device coupled between the dc input node and the switching node, the first switching device operative according to a first switching control signal, and
a second switching device coupled between the switching node and a constant voltage node, the second switching device operative according to a second switching control signal;
a switching control circuit operative in a first mode when the dc input voltage is less than a threshold voltage to provide the first and second switching control signals to operate the first and second switching devices to regulate the output voltage signal, the switching control circuit operative in a second mode when the dc input voltage is greater than the threshold voltage to provide the first switching control signal to turn off the first switching device; and
an active shunt circuit including a capacitor and a plurality of transistors operative according to at least one shunt circuit switching control signal to provide a shunt circuit output voltage signal to a shunt circuit output at a shunt circuit voltage level less than the dc input voltage in the second mode;
wherein the switching control circuit is operative in the second mode to provide the second switching control signal and the shunt circuit switching control signal to control the output voltage signal.
1. An integrated circuit, comprising:
a dc-DC converter circuit to control an output voltage signal, the dc-DC converter circuit including:
a first switching device coupled between a dc input node and a switching node, the first switching device operative according to a first switching control signal, and
a second switching device coupled between the switching node and a constant voltage node, the second switching device operative according to a second switching control signal;
an active shunt circuit including a shunt circuit input coupled to the dc input node, and a shunt circuit output, the active shunt circuit operative according to a shunt circuit switching control signal to provide a shunt circuit output voltage signal to the shunt circuit output at a shunt circuit voltage level less than the input voltage; and
a detector circuit including an input coupled to the dc input node, and an output to provide a mode control signal in a first state when an input voltage of the dc input node is less than a threshold voltage, the output operative to provide the mode control signal in a different second state when the input voltage of the dc input node is greater than the threshold voltage;
a switching control circuit operative in a first mode when the mode control signal is in the first state to provide the first and second switching control signals to operate the first and second switching devices to regulate the output voltage signal according to a feedback signal, the switching control circuit operative in a second mode when the mode control signal is in the second state to provide the first switching control signal to turn off the first switching device, and to provide the second switching control signal and the shunt circuit switching control signal to operate the active shunt circuit and the second switching device to control the output voltage signal.
2. The integrated circuit of
3. The integrated circuit of
4. The integrated circuit of
5. The integrated circuit of
6. The integrated circuit of
wherein the active shunt circuit includes:
a first transistor coupled between the dc input node and a first internal node, the first transistor operative according to a first shunt circuit switching control signal,
a second transistor coupled between the first internal node and the shunt circuit output, the second transistor operative according to a second shunt circuit switching control signal,
a third transistor coupled between the shunt circuit output and a second internal node, the third transistor operative according to a third shunt circuit switching control signal,
a fourth transistor coupled between the second internal node and the constant voltage node, the fourth transistor operative according to a fourth shunt circuit switching control signal, and
a capacitor coupled between the first and second internal nodes; and
wherein the switching control circuit is operative in the first mode to provide the shunt circuit switching control signals to turn off the first, second, third and fourth transistors, and wherein the switching control circuit is operative in the second mode to provide the shunt circuit switching control signals to provide the shunt circuit output voltage signal at the shunt circuit output at the shunt circuit voltage level less than the input voltage.
7. The integrated circuit of
wherein the switching control circuit is operative in the second mode to provide the shunt circuit switching control signals in a repeating sequence of a first phase, a second phase, and a third phase;
wherein the switching control circuit provides the shunt circuit switching control signals in the first phase to turn on the first and third transistors and turn off the second and fourth transistors to charge the capacitor through the shunt circuit output;
wherein the switching control circuit provides the shunt circuit switching control signals in the second phase to turn off the first, second, third and fourth transistors; and
wherein the switching control circuit provides the shunt circuit switching control signals in the third phase to turn off the first and third transistors and turn on the second and fourth transistors to discharge the capacitor through the shunt circuit output.
8. The integrated circuit of
wherein the switching control circuit is operative in the first mode to provide the third switching control signal to turn off the third switching device; and
wherein the switching control circuit is operative in the second mode to provide the second and third switching control signals to control the output voltage signal.
9. The integrated circuit of
10. The integrated circuit of
wherein the switching control circuit is operative in the second mode to provide the shunt circuit switching control signals in a repeating sequence of a first phase and a second phase;
wherein the switching control circuit provides the shunt circuit switching control signals in the first phase to turn on the first and third transistors and turn off the second and fourth transistors to charge the capacitor through the shunt circuit output; and
wherein the switching control circuit provides the shunt circuit switching control signals in the second phase to turn off the first and third transistors and turn on the second and fourth transistors to discharge the capacitor through the shunt circuit output.
11. The integrated circuit of
12. The integrated circuit of
13. The integrated circuit of
14. The integrated circuit of
a third switching device coupled between a dc input node and a switching node, the first switching device operative according to a first switching control signal, and
a second switching device coupled between the switching node and a constant voltage node, the second switching device operative according to a second switching control signal.
15. The integrated circuit of
a third switching device coupled between the dc input node and a second switching node, the third switching device operative according to a third switching control signal from the switching control circuit, and
a fourth switching device coupled between the second switching node and the constant voltage node, the fourth switching device operative according to a fourth switching control signal;
wherein the switching control circuit is operative in the first mode to provide the first, second, third and fourth switching control signals to operate the first, second, third and fourth switching devices to regulate the output voltage signal according to the feedback signal; and
wherein the switching control circuit is operative in the second mode to provide the first switching control signal to turn off the first switching device, to provide the third switching control signal to turn off the third switching device, and to provide the second switching control signal, the fourth switching control signal and the shunt circuit switching control signal to operate the active shunt circuit, the second switching device, and the fourth switching device to control the output voltage signal.
17. The power conversion system of
a first transistor coupled between the dc input node and a first internal node, the first transistor operative according to a first shunt circuit switching control signal,
a second transistor coupled between the first internal node and the shunt circuit output, the second transistor operative according to a second shunt circuit switching control signal,
a third transistor coupled between the shunt circuit output and a second internal node, the third transistor operative according to a third shunt circuit switching control signal, and
a fourth transistor coupled between the second internal node and the constant voltage node, the fourth transistor operative according to a fourth shunt circuit switching control signal;
wherein the capacitor is coupled between the first and second internal nodes;
wherein the switching control circuit is operative in the first mode to provide the shunt circuit switching control signals to turn off the first, second, third and fourth transistors;
wherein the switching control circuit is operative in the second mode to provide the shunt circuit switching control signals in a repeating sequence of a first phase, a second phase, and a third phase, the repeating sequence including providing the shunt circuit switching control signals in the first phase to turn on the first and third transistors and turn off the second and fourth transistors to charge the capacitor through the shunt circuit output, providing the shunt circuit switching control signals in the second phase to turn off the first, second, third and fourth transistors, and providing the shunt circuit switching control signals in the third phase to turn off the first and third transistors and turn on the second and fourth transistors to discharge the capacitor through the shunt circuit output.
18. The power conversion system of
wherein the active shunt circuit includes:
a first transistor coupled between the dc input node and a first internal node, the first transistor operative according to a first shunt circuit switching control signal,
a second transistor coupled between the first internal node and the shunt circuit output, the second transistor operative according to a second shunt circuit switching control signal,
a third transistor coupled between the shunt circuit output and a second internal node, the third transistor operative according to a third shunt circuit switching control signal,
a fourth transistor coupled between the second internal node and the constant voltage node, the fourth transistor operative according to a fourth shunt circuit switching control signal, and
wherein the capacitor is coupled between the first and second internal nodes;
wherein the switching control circuit is operative in the first mode to provide the third switching control signal to turn off the third switching device; and
wherein the switching control circuit is operative in the second mode to provide the second and third switching control signals to control the output voltage signal.
19. The power conversion system of
21. The power supply circuit of
22. The power supply circuit of
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The present disclosure relates generally to power conversion and more particularly to DC-DC converter circuits.
Switching regulators are used in a variety of applications to provide controlled DC output power by converting a DC input voltage. In automotive, industrial and aviation applications, a battery and alternator combination often provides the DC input voltage to a DC bus to power the DC-DC switching converter. In many automotive examples, the DC bus voltage ranges from 8-16 V, and buck DC-DC converters are used to provide 3.3 V or 5.0 V outputs to power motor control and other circuitry. However, high input voltage transient conditions may occur, for example, if the battery is disconnected, leading to a voltage rise on the DC bus. In this situation, the buck DC-DC converter high and low side switching devices may need to block voltages as high as 40 V or more during the high input voltage transient event. Accordingly, buck DC-DC converters used to supply 3.3-5.0 V outputs from 8-16 V inputs are designed with high and low side driver components capable of blocking 40 V. This leads to higher on-state resistance (e.g., FET RDSON) and switch capacitance due to higher rated devices. This results in increased on-state conduction and switching loss in normal operation due to the oversizing of the high and low side switches to accommodate the high input voltage transient possibility.
Disclosed examples include methods, power conversion systems, power supplies and integrated circuits with first and second switching devices connected to a switching node to control a DC output voltage signal. In normal operation in one example, the first and second switches operate as high and low side buck converter switches, and the switching node may be coupled to an output inductor to drive a load. When the DC input voltage exceeds a threshold voltage, the circuit enters a second mode in which a switching control circuit turns off the high side switch and engages a second supply circuit, such as an active shunt circuit, to provide a reduced voltage to continue converter operation to accommodate high input voltage transients. The low side switching device does not need to be oversized because the switching node is disconnected from the DC input voltage during high input voltage transients, and the threshold voltage can be set in certain examples to a level below the blocking voltage rating of the second switching device. In this manner, high-efficiency is facilitated during normal operation by reducing switching loss and conduction losses in the low side switch. In certain examples, the shunt circuit is a switched capacitor circuit including one or more transistors that are operated during shunt mode operation, with one or more capacitors charged and discharged through the output inductor. One or more of the shunt circuit transistors can be operated as a high side converter switch to continue DC-DC converter operation during high input voltage transient conditions, and the shunt circuit and the low side switch can be operated in open loop or closed loop fashion to maintain DC-DC converter operation until the transient condition ends and normal operation resumes. In certain examples, moreover, a third switch is provided between the shunt circuit output and the switching node, which is turned off during normal operation and enabled during transient operation to act as a high side converter switch.
In the drawings, like reference numerals refer to like elements throughout, and the various features are not necessarily drawn to scale. In the following discussion and in the claims, the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are intended to be inclusive in a manner similar to the term “comprising”, and thus should be interpreted to mean “including, but not limited to . . . ” Also, the term “couple” or “couples” is intended to include indirect or direct electrical connection or combinations thereof. For example, if a first device couples to or is coupled with a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via one or more intervening devices and connections.
V that receives a DC input voltage VDC, and provides a switching node 120 connected through an output inductor L to the output node 122. In certain examples, the inductor L can be included within the IC 100. In other examples, the inductor L is an external device outside the IC 100. As shown in
The IC 100 operates in a first mode, referred to herein as NORMAL mode, and a second mode, referred to herein as SHUNT mode. The DC-DC converter 101 includes a first switching device S1 operating in the normal mode as a high side switching device of a buck converter configuration, as well as a second switching device S2 operating as a low side switching device. Although the illustrated examples include buck converters, the various concepts of the present disclosure can be used in connection with other forms of DC-DC converter circuits 101, including without limitation buck converters, boost converters, buck-boost converters, cuk converters, etc. The switches S1 and S2 can be any suitable transistor switch, including without limitation field effect transistors (FETs), bipolar transistors, IGBTs, IGCTs, wide bandgap devices, etc. The switching devices S1 and S2 of the DC-DC converter circuit 101 are operated by control signals from a switching control circuit 104. In one example, the switching control circuit 104 includes a logic circuitry and driver circuits suitable for providing control signals to selectively turn on or off the switches S1 and S2, and the control circuit 104 includes further circuits to provide control signals to other circuitry in the IC 100. The first or high side DC-DC converter switch S1 is coupled between the DC input node 102 and the switching node 120, and is operated (e.g., closed or opened) according to a first switching control signal 106 from the PWM control circuit 104. The second switching device S2 is closed or opened according to a second switching control signal 108 from the control circuit 104.
In order to accommodate high input voltage transient conditions, the IC 100 includes a detector circuit 112 with an input coupled to the DC input node 102, as well as an auxiliary or second power supply circuit, such as a shunt circuit 110 connected in this example to the input node 102 and the switching node 120. The detector circuit 112 includes an input coupled to the DC input node 102, as well as an output 114 to provide a mode control signal SHON to the control circuit 104 in one example, the detector circuit 112 includes a voltage comparator (not shown) or other suitable circuitry to compare the input voltage VDC with a threshold voltage VTH. The threshold voltage VTH can be an internal reference circuit formed as part of the IC 100, or the IC 100 can include a terminal for connection of an external threshold voltage source to supply the threshold voltage VTH. In one example, the threshold voltage VTH is approximately 20 V. In certain examples, the threshold voltage VTH is less than the rated blocking voltage of the second switching device S2. As previously noted, for automotive or other applications in which the input voltage VDC may undergo overvoltage conditions and perhaps reach as high as 40 V, the low side switching device S2 would need to block this elevated DC voltage level. However, in the illustrated examples, the second switch S2 does not need to be oversized, and can be sized for blocking 20 V or lower. For a second switching device S2 capable of blocking 20 V, in one example, the threshold voltage VTH can be set to some level below 20 V. The detector circuit 112 provides the mode control signal SHON to the control circuit 104 in a first state (e.g., LO) when the input voltage VDC is less than or equal to the threshold voltage VTH, and provides the signal SHON in a second state (e.g., HI) when the input voltage VDC at the DC input node 102 is greater than the threshold voltage VTH.
The control circuit 104 in one example provides one or more shunt circuit switching control signals 116 to the shunt circuit 110 in response to receiving the mode control signal SHON in the second state. In this manner, the control circuit 104 switches to a second operating mode (SHUNT mode) and activates the shunt circuit 110 when the detector circuit 112 indicates that the DC input voltage VDC is undergoing an overvoltage transient event. In one example, the detector circuit 112 maintains the mode control signal SHON in the second state for as long as the input voltage VDC remains above the threshold voltage VTH. When the input voltage VDC is again less than or equal to the threshold voltage VTH, the detector circuit 112 resets the mode control signal SHON to the first state to place the control circuit 104 in the first operating mode (NORMAL mode). In one example, the control circuit 104 turns off all transistors of the active shunt circuit 110 in the first mode by providing one or more control signals 116 accordingly. In the first mode, moreover, the control circuit 104 operates the first and second switching devices S1 and S2 as high and low side switch is of a buck converter configuration in one example, to regulate the output voltage VO at the output node 122 according to one or more feedback signals. In one example, the control circuit 104 provides the switching control signals 106, 108 according to a voltage feedback signal VFB representing the output voltage VO and/or according to a current feedback signal IFB from a current sensor 124 in order to implement any suitable closed loop DC-DC converter regulation or control scheme, such as peak or valley current control, voltage regulation, etc. For example, the control circuit 104 may compare one or more feedback signals to a setpoint signal (not shown) to regulate the output voltage VO to a target level, such as 3.3 or 5.0 V.
The active shunt circuit 110 is operative according to the shunt circuit is operative according to one or more shunt circuit control signals 116 from the control circuit 104 to provide a shunt circuit output voltage signal at a voltage level less than the input voltage VDC. In the second operating mode (SHUNT mode) when the input voltage VDC exceeds the threshold voltage VTH, the shunt circuit 110 is activated by the control circuit 104, and provides a shunt circuit output voltage to the switching node 120 at approximately VDC/2 one example. The switching control circuit 104 is operative in the second mode to provide the first switching control signal 106 to turn off the first switching device S1. The switching node 120 of the buck converter example is therefore disconnected from the elevated DC input voltage VDC at the node 102. In the second mode, the switching control circuit 104 also provides the second switching control signal 108 and the shunt circuit switching control signal or signals 116 in order to operate the active shunt circuit 110 and the second switching device S2 in order to control the output voltage signal VO. In this manner, DC-DC conversion is continued throughout a high input voltage transient situation, with the second switch S2 continuing operation as a low side converter switch, and the shunt circuit 110 performing the high side switching functions at a voltage less than the elevated DC input voltage VDC. This, in turn, allows the second switch S2 to be sized according to efficiency considerations, with the selective operation of the shunt circuit 110 preventing the second switch S2 from having to block elevated DC voltages. In one example, for an automotive application having a nominal bus voltage in the range of 8-16 V, with the alternator 132 providing the potential for high input voltage excursions to approximately 40 V, the switching control circuit 104 operates in the second mode to provide the shunt circuit switching control signal(s) 116 to control the shunt circuit alters level at approximately half the input voltage (e.g., VDC/2=20 V in this example).
In other examples, the active shunt circuit 110 is operated according to the shunt circuit switching control signal or signals 116 to provide the shunt circuit output voltage signal at a level that is less than the input voltage VDC. In some examples, the shunt circuit 110 operates according to the signal or signals 116 in order to control the shunt circuit voltage level at a voltage less than a rated blocking voltage of the second switching device S2. Moreover, the threshold voltage VTH in one example is less than the rated blocking voltage of the switch S2. In this manner, the IC 100 in one example ensures that the low side switching device S2 does not need to block voltages greater than 20 V, allowing the switching loss and conduction loss reductions possible by sizing S2 according to the normal operation conditions, while still allowing continued operation of the DC-DC converter 101 in combination with the shunt circuit 110 during high input voltage transient situations.
Referring also to
The transistors QA, QB, QC and QD are operated according to corresponding first, second, third and fourth shunt circuit switching control signals 116-A, 116-B, 116-C and 116-D, respectively. In this example, the control circuit 104 provides the shunt circuit switching control signals 116 in the first mode to turn off the transistors QA-QD while providing the high and low side switching control signals 106 and 108 (curves 306 and 308, respectively, in
During SHUNT mode operation when the input voltage VDC is above the threshold voltage VTH, the control circuit 104 provides the control signals 116 in order to deliver the shunt circuit output voltage signal at the shunt circuit output node 203 at a level less than the input voltage VDC. The diagram 300 and
Referring to
In the second phase 320-2 of the second mode, the switching control circuit 104 provides the shunt circuit switching control signals 116 to turn off the transistors QA-QD of the shunt circuit 110, and provides the second switching control signal 108 to turn on Q2 (S2). As seen in
Continuing in
Then the detector circuit 112 transitions the signal SHON to the second state (HI) when the input voltage VDC exceeds VTH. In the second mode, the control circuit 104 turns off Q1 (S1), and continues to provide pulse width modulated switching control signal 108 to the second switch Q2 (S2), and provides pulse width modulated regulation of the output voltage VO by also providing the third switching control signal 900 to Q3 (S3) (curve 1110 in
Referring now to
The active shunt circuit 110 in this example includes a transistor QA connected between VDC (node 102) and a first internal node 1401, and a transistor QC connected between the node 1401 and a node 120A. In addition, the shunt circuit 110 includes a transistor Q2 the connected between a node 120B and a second internal node 1402, and a transistor QB connected between the node 1402 and the constant voltage node GND. The shunt circuit 110 also includes a floating or flying capacitor C-13 connected between the nodes 1401 and 1402. The control circuit 104 provides control signals 116 to operate the transistors QA-QD of the shunt circuit 110, including a signal 116-A to operate the transistor QA (curve 1516A in
In the second mode (SHUNT mode) when the mode control signal SHON goes high responsive to detection that the input voltage VDC exceeds the threshold VTH, the switching frequency remains the same and the control circuit 104 turns off the transistors Q1A and Q1B (signals 106A and 106B go LO). In addition, the control circuit 104 provides the signals 108A and 108B contemporaneously to provide low side inverter switching operation in alternating fashion with switched operation of an alternating pair or set of two of the shunt circuit transistors QA-QD. In particular, as shown in
The above examples are merely illustrative of several possible embodiments of various aspects of the present disclosure, wherein equivalent alterations and/or modifications will occur to others skilled in the art upon reading and understanding this specification and the annexed drawings. Modifications are possible in the described embodiments, and other embodiments are possible, within the scope of the claims.
Ramadass, Yogesh Kumar, Chakraborty, Sombuddha
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